As a huge fan of 2D side-scrolling platformers, looking at how beautifully a 2D world is constructed with art assets and motion designs has always been an enjoyable process. Among various details that constitute a coherent platformer experience, I often time find the camera movement being something that could instantly change the feel of the game. Cameras are the eyes with which we players perceive the game world, and given the lack of one dimension, it is of more significance to have a properly designed camera movement for 2D games since what players can see is already less than in a 3D experience.
While the camera movements in Super Mario being the one that players and designers often look at, there are other renown 2D platformers that in fact have very different designs that are worth looking at.
Super Mario Bros (1985)
In the classic Super Mario Bros, given that the level mainly expands horizontally, the camera will only move horizontally. The camera movement is affected by a camera window--the camera will only follow the player when the player reaches the edge of the window, in this case is roughly the center of the screen. When moving, the camera directly snaps to where the player is, meaning that there's no smooth movement or any slight delay. But players still perceive a smoothing effects because the movement of Mario himself has a fade-in and fade-out process. Interestingly, when players try to walk backwards in Super Mario Bros, the camera won't follow them to go back and therefore restricts how much players can go back.
Technically, it'll be a bit inaccurate to talk about Mega Man series as a whole since different games under the franchise have slightly different camera movement design. In the original Mega Man series, the levels are divided into chunks. A lot of chunks are just the same size as the camera view, and the camera would be still most of the time when players move inside a chunk. There are, however, some chunks of the level that are longer or taller than the camera view. In those chunks, the camera will directly follow the player in a linear fashion, placing the player almost at the center, until the camera reaches the edge of a chunk. When players go from one chunk to another chunk, the camera will entirely shift from one chunk to another before players can start moving.
In Mega Man Zero series, although the camera design is very similar to the original Mega Man, the levels are divided into bigger and less chunks. Therefore players experience a lot more camera movements than in the original Mega Man.
Ori and the Blind Forest & Hollow Knight
Ori and Hollow Knight, though their camera design is not exactly the same, do share a lot of common approaches when creating a more organic than mechanical camera movements. In both games, the camera movement is smooth, meaning that the camera smoothly travels from one point to another with some slight fade in and fade out effects, as opposed to linear movement which is what Mega Man uses. Both games also have inconsistent camera offsets, meaning that the relative position of the camera to the player can change depending on the area the player is in. This dynamic design allows designers to control what players can see at certain point of a level with more flexibility.
Comparing to Hollow Knight, one thing that Ori did and former did not do is the resizable camera view. This benefits the storytelling aspects when the designer intend to convey certain feelings.
So when you make your own 2D side-scrolling platformers, well, you could certainly invent your own camera movements, but how do you know where to start? Which one should you choose? The immediate answer would be to choose the one that "feels" right given the type of experience you are building.